Pumps are generally designed to operate at a nominal input voltage. A solenoid pump is an exemplary pump, which operates by energizing a solenoid to move a plunger back and forth within a cylinder to draw fluid from an inlet and discharge the fluid through an outlet of the cylinder. The energy applied to the solenoid determines how fast and for how long the plunger operates. If the energy exceeds a nominal amount, the plunger can reach its physical travel limit while energized, potentially reducing the life expectancy of the pump and wasting energy.
To enable a single voltage rated solenoid pump to operate at both nominal input voltages of 115 VAC and 230 VAC, the power delivered to the pump must be regulated. One method for regulating the alternating current (AC) power is by controlling conduction of a triode for alternating current (TRIAC) that energizes the solenoid as a function of the nominal input voltage so that power is not delivered during the entire positive half-cycle of the source power when the nominal input voltage is 230 VAC.
Prior approaches to detect the nominal input voltage used linear transformers to step-down the AC input voltage and voltage dividers to determine the voltage on the secondary winding of the transformer, which is then converted by the step-down factor to determine the nominal input voltage. Such transformers, however, are large (especially those rated up to 230 VAC) and may not be suitable for use in constrained spaces such as in mini-condensate pump applications. In another approach, a voltage divider is connected directly to the AC input voltage. However, such approach does not provide electrical isolation between the power circuit and the control circuit. Accordingly, an approach to nominal input voltage detection that overcomes these deficiencies is desirable.